In recent years, the amount of the information flowing through a network has been increased by the spread of a wide-band network, and the information processing capacity in the information equipment such as a router or a server has been required to be improved. The transmission rate limit of the electrical circuit board used in the equipment, however, constitutes the barrier against an improved equipment capacity. In order to break through this barrier and further improve the information processing capacity in the information equipment, optical interconnection of a plurality of boards accommodated in the equipment is effective. To implement the optical interconnection in the information equipment, a method is generally conceived in which a signal input/output board and a switch board are connected in the direction perpendicular to the optical backplane which optical transmission paths such optical fibers are laid thereon, and the electrical signal on the board is converted into an optical signal by a photoelectric conversion part and sent to the optical backplane, so that the optical signal of the optical backplane is converted into an electrical signal and returned to a board.
The structure for connecting the board to the optical backplane requires the ease of the device maintenance. Among the component elements used for optical interconnection by the optical backplane, the photoelectric conversion part is currently highest in failure rate. The device using the optical backplane, therefore, is required to have a mechanism in which the photoelectric conversion part can be easily replaced.
As a first conventional example, the mechanism described in Non-Patent Document 1 is known. The structure of this mechanism is shown in FIG. 17. FIG. 17 is a diagram showing a general structure. In FIG. 17, the optical fibers connected to a fiber management system 100 are connected to the optical connectors 102 passed through a backplane 101, and the optical connectors 102 are connected to the photoelectric conversion modules 104 arranged on a board 103. In the case where the photoelectric conversion module 104 gets out of order in this configuration, the whole board 103 with the photoelectric conversion modules 104 mounted thereon is replaced or, generally, the photoelectric conversion modules 104 mounted on the board by soldering are replaced by melting the solder using the soldering iron or the repair machine.
As another conventional example of the structure of the part for connecting the circuit board to the optical backplane, the mechanism described in Patent Document 1 is known, in which a board having at an end thereof an optical connector holding a LD (Laser Diode) and a PD (Photo Diode) is inserted into each of optical data buses including a slab optical waveguide, so that the optical data buses and each board are connected to each other optically. According to this prior art, the optical backplane is called the ‘optical data bus’. The general structure of the optical data buses is shown in FIG. 18, and the detailed optical connectors thereof in FIG. 19. The LD, PD accommodated in the CAN package are held in each optical connector 50, and the direction in which light is input/output to and from the LD, PD is perpendicular to the optical data buses 30. Each of the optical paths of the optical signals propagating through the optical data buses 30 is bent at the right angle by a 45′ mirror arranged on the end surface of each optical data bus 30 and optically coupled with the LD, PD. The electrical connection between LD, PD and the board PK is established by connecting the signal line 62 extending from LD, PD to a connector 64 arranged on each circuit board PK. A rod 56 of each optical connector 50 is arranged via a through hole H of an optical data bus fixing board 10 and a through hole 41h of the printed wiring board 40, so that the optical connectors 50, the optical data bus fixing board 10 and the printed wiring board 40 are set in position relatively. The optical data buses 30 are inserted into optical data bus inserting depressions 14 of the optical data bus fixing board 10. At both longitudinal ends of the upper end surface of an upper case 54, a pair of board fixing portions 60 for erecting the circuit boards PK are arranged. A signal processing IC 66 and an electrical connector 43 are arranged on each circuit board PK. The electrical connector 43 is connected to a corresponding electrical connector 42 of the printed wiring board 40. The optical connectors 50 each include a lower case 52 for accommodating a laser diode LD accommodated in a CAN package and a photodiode PD accommodated in the CAN package, and an upper case 54 fixed on the upper part of the lower case 52.    Non-Patent Document 1: Infineon PAROLI Backplane Solution, April 2003, page. 5 URL (http://www.infineon.com/cgi/ecrm.dll/ecrm/scripts/public_download.jsp?)    Patent Document 1: Japanese Unexamined Patent Publication No. 2003-283075